This invention relates to apparatus for observing the interior of a chimney during periods when the chimney is working to determine the burning operation of a stove being serviced by the chimney and for the condition of the chimney.
In U.S. Pat. No. 4,434,784 which issued to Van Patten on March 6, 1984, there is disclosed a chimney viewing system that is intended to be installed below a flue pipe leading into the chimney. The device consists of an airtight viewing window that is mounted in the chimney immediately below the flue entrance and a bracket mounted mirror positioned inside the chimney adjacent the window. A person outside the chimney looking through the window was thus provided an unimpeded view up the chimney whereby both the smoke column and the physical condition of the interior chimney surfaces can be observed while an associated stove or the like is working. As noted in this patent, smoke pattern can be used to adjust the stove to provide for optimum burning conditions and any defects in the chimney structure can be readily detected. This device has proven to be quite effective in practice and leads to a decrease in creosote buildup on the chimney and greater safety where the stove is used to burn wood.
Although the prior Van Patten device has proved to work quite well in practice it can only be installed where the chimney extends below the flue entrance. In many applications such as existing fireplaces, fireplaces equipped with stove inserts or free standing stoves using multiwall metal pipe chimneys, the underflue device can not be effectively utilized. Placing the mirror and mirror bracket in the flue chamber disturbes the drawing characteristics of the chimney. Furthermore, the mirror tends to become degraded by heat and quickly looses its reflecting capabilities. Lastly, a large access hole must be cut into the chimney which particularly in the case of a fireplace can be objectionable from an aesthetic stand point and might cause severe structural damage to the chimney.